It has been many years since it was first discovered that one could polymerize olefins using a catalyst comprising a transition metal compound and a co-catalyst comprising an organometallic reducing agent. Early on it was discovered that some benefits could be obtained by combining the transition metal compound with other particulate materials. One of the most often used particulate material has been magnesium chloride, particularly when the magnesium chloride is in an activated form. There are numerous patents disclosing how one can obtain an activated magnesium dichloride. Some examples are U.S. Pat. Nos. 4,315,836 and 4,542,198, the disclosures of which are incorporated herein by reference.
While the use of an activated magnesium chloride has generally been found to increase the activity of the catalyst, there are a number of other characteristics that need to be taken into account in order to obtain the most desirable catalysts. Some examples of these other characteristics include the settling rate of the catalyst, the final chlorine content of the catalyst, the density of the polymer produced with the catalyst, the bulk density of the polymer produced with the catalyst, and the molecular weight distribution of the polymer produced with the catalyst.
An object of the present invention is to provide an improved type of magnesium dihalide containing olefin polymerization catalyst. Other aspects, advantages, and benefits of the present invention will be apparent to one skilled in the art having the benefit of this disclosure.